Many modern automotive ignition systems are required to provide protection from excessively long dwell events, which are often the result of a system or wiring fault. If such excessively long dwell events are not detected and properly handled, serious damage to control electronics or the associated ignition coils may occur. Conventional automotive ignition systems consist of an interface control integrated circuit operable to control the operation of a power switching transistor configured to drive an associated ignition coil, wherein all such components may be combined in a single coil assembly.
Heretofore, conventional techniques for detecting excessively long dwell events, typically referred to as “over-dwell” events, has included the use of timing circuitry capable of monitoring dwell times ranging from tens to hundreds of milliseconds. Known timing circuitry capable of monitoring dwell times of such duration generally requires either an on-chip oscillator and counter, or an external timing capacitor. It is desirable in automotive ignition circuitry to implement an over-dwell protection function that does not strictly require either a complex integrated circuit design including oscillators and counters, or external timing capacitors.